A High Voltage Interlock Loop (HVIL) system and Control Strategy is provided for an alternative fuel vehicle including an electric, a hybrid electric, or a fuel cell vehicle. Generally, the HVIL system having associated logic including an HVIL circuit is provided to allow the vehicle to operate in either a high voltage (HV) or power mode powered by a power source or a HVIL interrupt mode based on an operational state of the HVIL system. When HVIL circuit fails shorted high, low or open, a Diagnostic Trouble Code (DTC) is set and the Service Soon Lamp is illuminated to indicate to a service technician that additional safety precautions need to be taken when servicing the HV system. The HV contactors may or may not be activated providing HV to the vehicle when HV is not expected to be present at connectors and HV devices.